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Pretest
1. What is energy?
2. What is mechanical energy?
3. True or False: Displacements in opposite directions add together.
4. How is speed calculated?
Chapter 17
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Pretest (continued)
5. What are the standard units of distance and time?
6. Which is longer, 0.25 m or 25 m?
7. What happens to the spacing of the particles within a solid or liquid as the temperature increases?
Chapter 17
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Pretest (continued)
8. What happens to the speed of the particles in a solid, liquid, or gas as the temperature is increased?
9. If a car takes 2 hrs to travel 100 km, what is its average speed?
a. 25 km/h b. 50 km/hc. 75 km/hd. 100 km/h
Chapter 17
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Interest Grabber
VibrationsA wave is a vibration that carries energy from one place to another. But not all vibrations are waves.
Hold a pen lightly between your thumb and index finger. Shake your hand back and forth to make the pen seem to bend like it’s made of rubber. Next, hold a length of string (about 1 meter long) at one end. Shake the end of the string back and forth. Observe the vibrations.
1. Describe the motion of the pen and the motion of the string.
2. In which case did the vibration move from one place to another? In which case did the vibration stay in one place?
Section 17.1
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Reading Strategy
Previewing
Section 17.1
a. Troughs
b. Rest position
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Transverse Waves Figure 2
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Transverse Waves Figure 2
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Transverse Waves Figure 2
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Longitudinal Waves Figure 3
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Longitudinal Waves Figure 3
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Surface Waves Figure 4
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Surface Waves Figure 4
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Surface Waves Figure 4
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Surface Waves Figure 4
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Surface Waves Figure 4
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Interest Grabber
Waves Carry EnergyWhen a wave travels through a medium, the wave carries energy, not particles, from one place to another. You can measure the speed of a wave by how fast energy moves from one place to another.
To model a wave’s energy transfer, stand in a line with your classmates. The first person in the line should slowly pass a book to the second person. The second person should pass it to the third person, and so on down the line. Repeat the activity, but this time pass the book quickly.
1. What did the book represent?
2. How would you describe the speed of the wave in each case?
Section 17.2
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Reading Strategy
Building Vocabulary
Section 17.2
a. The time required for one cycleb. The number of complete cycles in a given timec. The distance between a point on a wave and the same point on the next cycle of the waved. The maximum displacement of a medium from its rest position
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Frequency and Wavelength of Transverse Waves
Figures 5 and 6
Frequency
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Frequency and Wavelength of Transverse Waves
Figures 5 and 6
Frequency Wavelength
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Speed of Mechanical Waves
Section 17.2
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Speed of Mechanical Waves
Section 17.2
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Speed of Mechanical Waves
Section 17.2
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Speed of Mechanical Waves
Section 17.2
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Amplitude of Transverse Waves
Section 17.2
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Interest Grabber
Reflected WavesWhat happens when a wave hits a wall or some other fixed object? To find out, tie a rope to the back of a chair. Gently shake the rope up and down once to send a single pulse along the rope as shown. Observe what happens when the pulse hits the chair.
1. What happened to the direction of the pulse when it hit the chair?
2. How did the orientation of the reflected pulse compare to the original pulse?
Section 17.3
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Reading Strategy
a. If reflection occurs at a fixed boundary, the reflected wave will be upside down compared to the original wave.
b. Refraction occurs when a wave enters a new medium at an angle because one side of a wave front moves more slowly than the other side.
c. The larger the wavelength is compared to the size of an opening or obstacle, the more a wave diffracts.
d. The types of interference are constructive and destructive interference.
e. A standing wave forms only if a multiple of one half wavelength fits exactly into the length of the vibrating object.
Section 17.3
Identifying Main Ideas
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Constructive vs. Destructive Interference of Waves
Figure 12
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Constructive vs. Destructive Interference of Waves
Figure 12
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Constructive vs. Destructive Interference of Waves
Figure 12
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Constructive vs. Destructive Interference of Waves
Figure 12
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Interest Grabber
Can You Hear Through Your Desk?Sound waves travel through a medium as energy is passed from particle to particle. If the particles are close together, as in a solid, the sound generally travels faster and less energy is lost.
Listen carefully to the sound as you knock on your desk. Note how far your ear is from your hand when you make the sound. Without changing this distance, place your ear against your desk and knock again.
1. In each case, how did the sound travel to your ears?
2. What was the difference in the sound when you held your ear against the desk?
Section 17.4
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Reading Strategy
a. intensity and loudness
b. frequency and pitch
Section 17.4
Using Prior Knowledge
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The Speed of Sound in Different Mediums
Figure 14
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The Speed of Sound in Different Mediums
Figure 14
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The Speed of Sound in Different Mediums
Figure 14
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The Speed of Sound in Different Mediums
Figure 14
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The Doppler Effect Figure 18
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The Anatomy of the Ear
Figure 19
Pretest Answers
1. What is energy?
2. What is mechanical energy?
3. True or False: Displacements in opposite directions add together.
4. How is speed calculated?
Chapter 17
Click the mouse button to display the answers.
The ability to do work.
The energy due to the motion or position of an object.
distance/time
Displacement in opposite directions subtract.
Chapter 17Pretest Answers (continued)
Click the mouse button to display the answers.
5. What are the standard units of distance and time?
6. Which is longer, 0.25 m or 25 m?
7. What happens to the spacing of the particles within a solid or liquid as the temperature increases?
meters and seconds
25 m
The particles move farther apart.
Chapter 17
Click the mouse button to display the answers.
Pretest Answers (continued)
8. What happens to the speed of the particles in a solid, liquid, or gas as the temperature is increased?
9. If a car takes 2 hrs to travel 100 km, what is its average speed?
a. 25 km/h b. 50 km/hc. 75 km/hd. 100 km/h
The particles move faster.
Interest GrabberAnswers
1. Describe the motion of the pen and the motion of the string.
The pen’s motion blurred as it vibrated back and forth. The string had a series of S-shaped curves that traveled along the string.
2. In which case did the vibration move from one place to another? In which case did the vibration stay in one place?
The pen vibrated in place. The vibrations moved along the string from one end to the other.
Section 17.1
Interest GrabberAnswers
1. What did the book represent?
The book represented energy being transferred by a wave. Some students may answer that the book represents a crest of the wave.
2. How would you describe the speed of the wave in each case?
The energy (or crests) moved faster when the books were passed faster.
Section 17.2
Interest GrabberAnswers
1. What happened to the direction of the pulse when it hit the chair?
The pulse bounced off the chair; it reversed direction as it traveled back along the rope.
2. How did the orientation of the reflected pulse compare to the original pulse?
The pulse was turned upside down by the reflection.
Section 17.3
Interest GrabberAnswers
1. In each case, how did the sound travel to your ears?
At first, the sound had to travel through air to reach your ears. When you held your ear to the desk, the sound traveled to your ear through the solid desk.
2. What was the difference in the sound when you held your ear against the desk?
The sound was louder when heard through the solid material.
Section 17.4
Chapter 17Go Online
More on the issue of protecting whales fromnoise pollution
Self-grading assessment
Articles on sound
For links on vibrations and waves, go to www.SciLinks.org and enter the Web Code as follows: ccn-2171.
For links on wave properties, go to www.SciLinks.org and enter the Web Code as follows: ccn-2172.
For links on diffraction and interference, go to www.SciLinks.org and enter the Web Code as follows: ccn-2173.
